Nitrogen Filled Tires

**snoopy0812** · 11-10-2009 08:43 PM

ok so I've been getting told to get nitrogen filled tires because it'll make my tires last longer and because nitrogen molecules are bigger they don't "seep" through sidewalls and stuff and leak as bad.. but before I shilled out cash to do this I thought I'd do some research.

I've decided that breaking it down into the 3 most common claims would be the easiest method of figuring out cost vs. value.

Claim #1
"Fill up your tires with Nitrogen and you can save up to 6% on your fuel mileage"

Fact:
Any properly maintained tire with regards to tire pressure will keep your fuel economy optimal for tire related fuel economy.

Claim #2
"Nitrogen is a Large Molecule, Air will seep from rubber at a rate of 2.5 pounds per month. Nitrogen will maintain this pressure longer, at a rate of only 0.5 per month."

Fact:
"Air" is usually over 70% nitrogen to start with. Nitrogen is larger than Oxygen which is usually called "air".
Oxygen has a density of 1.429 g/L (measured conditions:0 °C, 101.325 kPa)
Nitrogen has a density of 1.251 g/L in the same conditions.
Armed with that information a Nitrogen molecule does indeed occupy more space than an Oxgen molecule but only about 0.00000000003 meters more. So it does make it harder for nitrogen to escape rubber, it does not make it imposible nor does it make it 5 times less likely to permeate. Permeation would be determined by the quailty of the rubber used in the tired. Nitrogen is lighter than oxygen but it will not shave a second off your 1/4 mile.

Claim #3
"Nitrogen is Dry. This eliminates Rim Corrosion, preserves Steel Belts, and minimizes pressure swings in Hot and Cold temperatures."

Fact:
Of course "Nitrogen is dry" it's a gas and when in a 99.99% state there could only be 0.01% of H20 which is water. Nitrogen does not enter a liquid state until -195.8 Celcius, at that temperature you're most likely not going to be alive to care if there is moisture inside your tire, which would have already crystalized into ice at 0.01 celcius. In an atmostphere such as a nitrogen filled tire, you would not get oxidization due to the obvious lack of oxygen.

Conclusion:
While their claims may seem like they've invented some sort of magic tire gas that'll fix every problem you've ever had with your tires, it turns out that it's a lot of common sense and a little bit of science. Nitrogen in quality tires should seep less than regular compressed air, by seeping less it should help keep your tire pressure reletively constant aiding in your fight against high fuel costs and due to your tires being filled with in a higher percent with nitrogen it will aid as an anti-oxidiser.
However, tire tread still gets that nasty oxygen so the outside will still degrade and unless you create a vacume on the inside of the tire while it's seated you won't get it completely filled with nitrogen getting the most postive effects.

Regarding another claim is that you will recieve less of a tire pressure change by using nitrogen when outside temperatures vary (i.e. -6 in the morning leaving for work but +12 when going home). This claim is much more difficult to elaborate on and from what I've read is a large issue for debate, i'm not wanting to argue with no one, I'm just posting info, you find something to the contrary I'll read it if you post link.
All gases expand at the same rate, however they do not expand at the same volume. The example for this debate is nitrogen vs. oxygen/air (which is appx 70% nitrogen, 20% oxygen, 10% other). If you have 1 litre of nitrogen and 1 litre of oxygen and going by above mentioned pressures and temperatures, if you increase the temperature the gas will expand increasing it's volume and in a sealed container its pressure. Because we know they they expand at the same rate, but their volumes will be different because their densities are not similar when you change the temperature from 0 to +5 the oxygen will have increased it's volume more than the nitrogen because it has more matter to expand. A larger increase in volume means it will exert more pressure. Therefore if you live somewhere that is subject to large changes in temperature and you want to deal with less of the effects of tire pressure changes, nitrogen is the way to go. But if you live somewhere where your climate is rather consistant (Cali, Florida, the North Pole) this aspect of nitrogen filling is rather moot. How much your tire pressure will change with nitrogen I don't know, but it will be less than with breathable air. And again it depends on the overall quality of your tires because when you have cold tires the rubber shrinks then it expands as you drive to warm them up again changing your tire pressure.

Sources:
http://www.getnitrogen.org/pdf/graham.pdf
Water - Wikipedia, the free encyclopedia
Oxygen - Wikipedia, the free encyclopedia
Nitrogen - Wikipedia, the free encyclopedia
Equation of state - Wikipedia, the free encyclopedia

**Pmastron** · 11-10-2009 10:01 PM

Awesome job! Living in Florida I've always said it was a waste of money

**CMcCane** · 11-11-2009 07:50 AM

Great informative article but I get free Nitrogen tire refills from my dealership for life so it can't hurt? lol

**preston_nfs** · 11-11-2009 08:03 AM

Originally Posted by CMcCane

Great informative article but I get free Nitrogen tire refills from my dealership for life so it can't hurt? lol

I get free Nitrogen also, so I use it.

**only1db** · 11-11-2009 08:06 AM

you did forget the expansion rate....when the tire heats up air pressure increases...this does not happen with the nitro

**snoopy0812** · 11-11-2009 12:23 PM

"Regarding another claim is that you will recieve less of a tire pressure change by using nitrogen when outside temperatures vary (i.e. -6 in the morning leaving for work but +12 when going home). This claim is much more difficult to elaborate on and from what I've read is a large issue for debate, i'm not wanting to argue with no one, I'm just posting info, you find something to the contrary I'll read it if you post link.
All gases expand at the same rate, however they do not expand at the same volume. The example for this debate is nitrogen vs. oxygen/air (which is appx 70% nitrogen, 20% oxygen, 10% other). If you have 1 litre of nitrogen and 1 litre of oxygen and going by above mentioned pressures and temperatures, if you increase the temperature the gas will expand increasing it's volume and in a sealed container its pressure. Because we know they they expand at the same rate, but their volumes will be different because their densities are not similar when you change the temperature from 0 to +5 the oxygen will have increased it's volume more than the nitrogen because it has more matter to expand. A larger increase in volume means it will exert more pressure. Therefore if you live somewhere that is subject to large changes in temperature and you want to deal with less of the effects of tire pressure changes, nitrogen is the way to go. But if you live somewhere where your climate is rather consistant (Cali, Florida, the North Pole) this aspect of nitrogen filling is rather moot. How much your tire pressure will change with nitrogen I don't know, but it will be less than with breathable air. And again it depends on the overall quality of your tires because when you have cold tires the rubber shrinks then it expands as you drive to warm them up again changing your tire pressure."

nope didn't forget it, you must have missed it but here ya go, I reposted it for ya.
All gasses expand when heated and all gasses expand at the same rate, however their volume or the amount of space they take up when they expand is different because it's different gasses. Because their relative volumes are different the amount of pressure created in a container will also be different. Hence most people think Nitrogen won't change pressure when the tire heats up, it does, just a smaller amount than air. What the exact pressure vs. temp changes are I can't compare so I can't and won't tell you that it's a fact that "air will increase 5 psi when your tires heat up and nitrogen will only increase 1 psi" because that wouldn't be fact. If you would like you can test it or if you find out the exact heat relative volume expansion with a given amount of nitrogen and air I'm sure I could calculate what the PSI change would be.

example of what it means volume of gas vs. pressure:

Fact: Propane expands from liquid to gas at a rate of 40 to 1.

So if I have 1 cubic foot of liquid propane in a container my approx pressure is about 250-300 psi at room temperature (21 celcius). If I release the propane to atmosphere it will occupy 40 cubic feet of space but it's pressure will be atmospheric. This is all given we have a controlled environment in a sealed vacume. Because of this massive expansion rate thats why propane is so dangerous.. a 500 gallon propane tank could generate at least 20,000 gallons of fire if a large enough hole was created in the tank, not to mention the shockwave of the rapid expansion of the gas.

How this applies to tires: We're not changing states (air/nitrogen remains gas) so drastic expansion will not happen. Our containers will remain the same appx size. Expansion is based primarily on temperature variences. Expansion is directly related to pressure.

Bottom line: Increase tire temp gas will expand, how much? I don't know. If someone has a relatively moderate day, takes a thermal gun and measures their tire temp before they drive, and then their tire pressure. Record those numbers and then heat up their tires (burn outs would mostly increase tire surface temperatures not overall tire temp which is what we would need) and re-measure their temps and pressure, you could find out a relative expansion rate.

**kpbboyed** · 11-11-2009 12:38 PM

wow~...too long.. something about nitrogen gas on ur tires... so.....what's the final conclusion... i didn't want to read the whole..thing....LOL Lazy...

so now...i go put some nitrogen gas on my tires???

**snoopy0812** · 11-11-2009 03:52 PM

no no... not ON your tires, IN your tires.. and I'm not saying to or not to, I just posted the info so people can decide if it's worth it or not. It's really a per location, per car, per person decision.

**Wisenos** · 12-13-2009 02:13 PM

Originally Posted by snoopy0812

no no... not ON your tires, IN your tires.. and I'm not saying to or not to, I just posted the info so people can decide if it's worth it or not. It's really a per location, per car, per person decision.

i'll do it next spring before putting back alloys onthe car

**coupegirl** · 12-13-2009 06:21 PM

I have a head ache I will go rest and read it again later

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